Surface modifications of poly (1, 4-phenylene-cis-benzobisoxazole) (PBO) fibres by coaxial atmospheric dielectric barrier discharge (PLA-PLA) have been studied in this paper. The mixture of argon and oxygen was used as inlet gas. The modification effects were examined by means of scanning electron microscopy (SEM), contact angle measurement (CA), the fourier transform infrared spectroscopy (FTIR) and the interlaminar shear strength (ILSS) measurement. The results indicated that the surface of treated PBO fibres became rougher compared to the untreated, and the contact angle decreased significantly by 25.03% from 84.7°to 63.5°after Ar/O2 plasma treatment for 3 minutes. The FTIR spectra showed that the polar functional groups were introduced into the surface of the PBO fibres after the treatment. Therefore, the interlaminar shear strength (ILSS) of PBO/D03E composite could be improved from 3.3 to 7.6 MPa.